text: /* Filename: colrops.c
   * Created by:  
   *
   * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
   *
   * PANDA 3D SOFTWARE
   * Copyright (c) Carnegie Mellon University.  All rights reserved.
   *
   * All use of this software is subject to the terms of the revised BSD
   * license.  You should have received a copy of this license along
   * with this source code in a file named "LICENSE."
   *
   * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
  
  /*
   * Integer operations on COLR scanlines
   */
  
  #include "color.h"
  
  #ifndef NULL
  #define NULL            0
  #endif
  
  #define bmalloc malloc
  #if !defined(WIN32_VC) && !defined(WIN64_VC)
  extern char     *bmalloc(int);
  #else
  #include <malloc.h>
  #include <math.h>
  #endif
  
  #define MAXGSHIFT       31              /* maximum shift for gamma table */
  
  static BYTE     *g_mant = NULL, *g_nexp = NULL;
  
  static BYTE     (*g_bval)[256] = NULL;
  
  #ifndef pow
  #if !defined(WIN32_VC) && !defined(WIN64_VC)
  extern double   pow(double, double);
  #endif
  #endif
  
  
  int setcolrcor(double (*f)(double, double), double a2)
                  /* set brightness correction */
  {
          double  mult;
          int    i, j;
                                          /* allocate tables */
          if (g_bval == NULL && (g_bval =
                          (BYTE (*)[256])bmalloc((MAXGSHIFT+1)*256)) == NULL)
                  return(-1);
                                          /* compute colr -> gamb mapping */
          mult = 1.0/256.0;
          for (i = 0; i <= MAXGSHIFT; i++) {
                  for (j = 0; j < 256; j++)
                          g_bval[i][j] = (BYTE) (256.0 * (*f)((j+.5)*mult, a2));
                  mult *= 0.5;
          }
          return(0);
  }
  
  
  int setcolrinv(double (*f)(double, double), double a2)
                  /* set inverse brightness correction */
  {
          double  mult;
          int    i, j;
                                          /* allocate tables */
          if (g_mant == NULL && (g_mant = (BYTE *)bmalloc(256)) == NULL)
                  return(-1);
          if (g_nexp == NULL && (g_nexp = (BYTE *)bmalloc(256)) == NULL)
                  return(-1);
                                          /* compute gamb -> colr mapping */
          i = 0;
          mult = 256.0;
          for (j = 255; j > 0; j--) {
                  while ((g_mant[j] = (BYTE)(mult * (*f)(j/256.0, a2))) < 128) {
                          i++;
                          mult *= 2.0;
                  }
                  g_nexp[j] = i;
          }
          g_mant[0] = 0;
          g_nexp[0] = COLXS;
          return(0);
  }
  
  
  int setcolrgam(double g)                        /* set gamma conversion */
  {
          if (setcolrcor(pow, 1.0/g) < 0)
                  return(-1);
          return(setcolrinv(pow, g));
  }
  
  
  int colrs_gambs(COLR *scan, int len)
                  /* convert scanline of colrs to gamma bytes */
  {
          int    i, expo;
  
          if (g_bval == NULL)
                  return(-1);
          while (len-- > 0) {
                  expo = scan[0][EXP] - COLXS;
                  if (expo < -MAXGSHIFT) {
                          if (expo < -MAXGSHIFT-8) {
                                  scan[0][RED] =
                                  scan[0][GRN] =
                                  scan[0][BLU] = 0;
                          } else {
                                  i = (-MAXGSHIFT-1) - expo;
                                  scan[0][RED] =
                                  g_bval[MAXGSHIFT][((scan[0][RED]>>i)+1)>>1];
                                  scan[0][GRN] =
                                  g_bval[MAXGSHIFT][((scan[0][GRN]>>i)+1)>>1];
                                  scan[0][BLU] =
                                  g_bval[MAXGSHIFT][((scan[0][BLU]>>i)+1)>>1];
                          }
                  } else if (expo > 0) {
                          if (expo > 8) {
                                  scan[0][RED] =
                                  scan[0][GRN] =
                                  scan[0][BLU] = 255;
                          } else {
                                  i = (scan[0][RED]<<1 | 1) << (expo-1);
                                  scan[0][RED] = i > 255 ? 255 : g_bval[0][i];
                                  i = (scan[0][GRN]<<1 | 1) << (expo-1);
                                  scan[0][GRN] = i > 255 ? 255 : g_bval[0][i];
                                  i = (scan[0][BLU]<<1 | 1) << (expo-1);
                                  scan[0][BLU] = i > 255 ? 255 : g_bval[0][i];
                          }
                  } else {
                          scan[0][RED] = g_bval[-expo][scan[0][RED]];
                          scan[0][GRN] = g_bval[-expo][scan[0][GRN]];
                          scan[0][BLU] = g_bval[-expo][scan[0][BLU]];
                  }
                  scan[0][EXP] = COLXS;
                  scan++;
          }
          return(0);
  }
  
  
  int gambs_colrs(COLR *scan, int len)
          /* convert gamma bytes to colr scanline */
  {
          int    nexpo;
  
          if (g_mant == NULL || g_nexp == NULL)
                  return(-1);
          while (len-- > 0) {
                  nexpo = g_nexp[scan[0][RED]];
                  if (g_nexp[scan[0][GRN]] < nexpo)
                          nexpo = g_nexp[scan[0][GRN]];
                  if (g_nexp[scan[0][BLU]] < nexpo)
                          nexpo = g_nexp[scan[0][BLU]];
                  if (nexpo < g_nexp[scan[0][RED]])
                          scan[0][RED] = g_mant[scan[0][RED]]
                                          >> (g_nexp[scan[0][RED]]-nexpo);
                  else
                          scan[0][RED] = g_mant[scan[0][RED]];
                  if (nexpo < g_nexp[scan[0][GRN]])
                          scan[0][GRN] = g_mant[scan[0][GRN]]
                                          >> (g_nexp[scan[0][GRN]]-nexpo);
                  else
                          scan[0][GRN] = g_mant[scan[0][GRN]];
                  if (nexpo < g_nexp[scan[0][BLU]])
                          scan[0][BLU] = g_mant[scan[0][BLU]]
                                          >> (g_nexp[scan[0][BLU]]-nexpo);
                  else
                          scan[0][BLU] = g_mant[scan[0][BLU]];
                  scan[0][EXP] = COLXS - nexpo;
                  scan++;
          }
          return(0);
  }
  
  
  void
  shiftcolrs(COLR *scan, int len, int adjust)
          /* shift a scanline of colors by 2^adjust */
  {
          int     minexp;
  
          if (adjust == 0)
                  return;
          minexp = adjust < 0 ? -adjust : 0;
          while (len-- > 0) {
                  if (scan[0][EXP] <= minexp)
                          scan[0][RED] = scan[0][GRN] = scan[0][BLU] =
                          scan[0][EXP] = 0;
                  else
                          scan[0][EXP] += adjust;
                  scan++;
          }
  }
  
  
  void
  normcolrs(COLR *scan, int len, int adjust)
  /* normalize a scanline of colrs */
  {
          int  c;
          int  shift;
  
          while (len-- > 0) {
                  shift = scan[0][EXP] + adjust - COLXS;
                  if (shift > 0) {
                          if (shift > 8) {
                                  scan[0][RED] =
                                  scan[0][GRN] =
                                  scan[0][BLU] = 255;
                          } else {
                                  shift--;
                                  c = (scan[0][RED]<<1 | 1) << shift;
                                  scan[0][RED] = c > 255 ? 255 : c;
                                  c = (scan[0][GRN]<<1 | 1) << shift;
                                  scan[0][GRN] = c > 255 ? 255 : c;
                                  c = (scan[0][BLU]<<1 | 1) << shift;
                                  scan[0][BLU] = c > 255 ? 255 : c;
                          }
                  } else if (shift < 0) {
                          if (shift < -8) {
                                  scan[0][RED] =
                                  scan[0][GRN] =
                                  scan[0][BLU] = 0;
                          } else {
                                  shift = -1-shift;
                                  scan[0][RED] = ((scan[0][RED]>>shift)+1)>>1;
                                  scan[0][GRN] = ((scan[0][GRN]>>shift)+1)>>1;
                                  scan[0][BLU] = ((scan[0][BLU]>>shift)+1)>>1;
                          }
                  }
                  scan[0][EXP] = COLXS - adjust;
                  scan++;
          }
  }
  